The ninth Ava is a day a post and mourning. Tragical events are connected Jews in this day.
This day the Jews left the Egyptian slavery and directed in the Land of Israel , have believed the scouts sent forward as if to win this ground it is impossible. That people has doubted of power Supreme, he has been punished by the G-d: Jews should wander 40 years on desert, all sinned generation will not die out yet.
This day is connected to destruction the Temple . 9 Ava 586 up to AD Babylon armies the First Temple has been destroyed. 9 Ava 70 up to AD the Roman army has grasped and has destroyed the Second Temple. Later some years, too 9 Ava, a place on which there was a Temple, have been ploughed up. Subsequently there the new, pagan city - Elia Capitolina has been constructed.